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Global Call IP Technology Guide — November 2007 95
Dialogic Corporation
IP Call Scenarios
3.3.6.6 Party B Drops Transferred Call Early
Figure 38 illustrates a scenario in which the Transferee (party B) drops the transferred call before
receiving a response to the INVITE it sent to party C. As a result, the
GCEV_INVOKE_XFER_FAIL termination event is received at the Transferor (party A) and the
GCEV_XFER_FAIL termination event is received a the Transferee (party B). The original primary
call is left connected and in the GCST_CONNECTED state from the perspective of both A and B.
Figure 38. SIP Call Transfer Failure - Party B Drops Transferred Call Early
A
(Transferring,
Transferor)
App
A
(Transferring,
Transferor)
IP CCLib
B
(Transferred,
Transferee)
App
B
(Transferred,
Transferee)
IP CCLib
C
(Transferred To,
Transfer Target)
App
C
(Transferred To,
Transfer Target)
IP CCLib
GCEV_REQ_
XFER(CRNp)
Pre condition: Primary call between A and B is connected (not shown).
202 Accepted
GCEV_ACCEPT_
XFER(CRNp)
GCEV_
INVOKE_XFER_
ACCEPTED(CRNp)
NOTIFY(100 Trying)
Subscription-State=active; expires=300
200 OK
REFER
gc_InvokeXfer
(CRNp)
INVITE
GCEV_OFFERED
(CRNt)
gc_MakeCall
(CRNt, CRNp)
GCEV_
DISCONNECTED
(CRNt)
...before C answers...
gc_AcceptXfer
(CRNp)
GCEV_DROPCALL
(CRNt)
gc_ReleaseCallEx
(CRNt)
GCEV_RELEASECALL
(CRNt)
GCEV_XFER_FAIL
(CRNp)
gc_DropCall(CRNt)
Parties A and B remain connected.
Post condition:
Cause = IPEC_SIPReasonStatus487RequestTerminated
NOTIFY (487 Request Terminated)
Subscription-State = terminated
200 OK
Cause = IPEC_SIPReasonStatus487RequestTerminated
GCEV_DROPCALL
(CRNt)
gc_ReleaseCallEx
(CRNt)
GCEV_RELEASECALL
(CRNt)
gc_DropCall(CRNt)
GCEV_
INVOKE_XFER_
FAIL(CRNp)
GCEV_DISCONNECTED
(CRNt)
gc_DropCall(CRNt)
CANCEL
ACK (INVITE)
200 OK (CANCEL)
487 Request Terminated (INVITE)